WTF?

HAI  
I HAS A TUX  
GIMMEH TUX  
I HAS A FOO ITS 0  
I HAS A BAR ITS 0  
I HAS A BAZ ITS 0  
I HAS A QUZ ITS 1  
TUX IS NOW A NUMBR  
IM IN YR LOOP NERFIN YR TUX TIL BOTH SAEM TUX AN 0  
I HAS A PUR  
GIMMEH PUR  
PUR IS NOW A NUMBR  
FOO R SUM OF FOO AN PUR  
BAR R SUM OF BAR AN 1  
BOTH SAEM BIGGR OF PRODUKT OF FOO AN QUZ AN PRODUKT OF BAR BAZ AN PRODUKT OF FOO AN QUZ  
O RLY?  
YA RLY  
BAZ R FOO  
QUZ R BAR  
OIC  
IM OUTTA YR LOOP  
BAZ IS NOW A NUMBAR  
VISIBLE SMOOSH QUOSHUNT OF BAZ QUZ  
KTHXBYE  

Input

The input contains between 1 and 10 lines, i-th line contains an integer number xi (0 ≤ xi ≤ 9).

Output

Output a single real number. The answer is considered to be correct if its absolute or relative error does not exceed 10 - 4.

Examples

Input

3 0 1 1

Output

0.666667

inputFormat

Input

The input contains between 1 and 10 lines, i-th line contains an integer number xi (0 ≤ xi ≤ 9).

outputFormat

Output

Output a single real number. The answer is considered to be correct if its absolute or relative error does not exceed 10 - 4.

Examples

Input

3 0 1 1

Output

0.666667

样例

3
0
1
1

0.666667

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